Artificial disc system

ABSTRACT

An artificial replacement disc includes a pair of substantially parallel plates formed to occupy a space defined by vertebral endplates, each of the plates including a plurality of spikes on a first surface and a concave trough formed on a second surface opposite of the first surface. A mobile core includes a core rim with opposing convex surfaces extending from opposite sides of the core rim, the mobile core being capable of being disposed between the pair of plates to permit the vertebral endplates to move relative to one another. The spikes on each of the plates extend substantially away from the mobile core and the convex surfaces are formed to integrally fit within the concave trough of at least one of the plates. The core rim limits lateral movement of the mobile core relative to the parallel plates. One or more insertion tools for inserting and implanting the replacement disc are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.15/970,406, filed Jan. 12, 2018 (now U.S. Pat. No. 10,610,371) which isa Continuation of U.S. application Ser. No. 14/739,327, filed Jun. 15,2015, which is a Continuation of U.S. application Ser. No. 13/893,326,filed May 13, 2013 (now U.S. Pat. No. 9,056,018), U.S. application Ser.No. 11/943,334, filed Nov. 20, 2007 (now U.S. Pat. No. 8,535,379), U.S.application Ser. No. 10/964,633, filed Oct. 15, 2004, and aContinuation-in-part of U.S. application Ser. No. 11/487,415, filed Jul.17, 2006 (now U.S. Pat. No. 7,854,766) and U.S. application Ser. No.11/019,351, filed Dec. 23, 2004 (now U.S. Pat. No. 7,083,650).

U.S. application Ser. No. 13/893,326 is a Continuation of U.S.application Ser. No. 11/943,334, filed Nov. 20, 2007 (now U.S. Pat. No.8,535,379) and U. S. application Ser. No. 10/964,633, filed Oct. 15,2004 and a Continuation-in-part of U.S. application Ser. No. 11/487,415,filed Jul. 17, 2006 (now U.S. Pat. No. 7,854,766) and U.S. applicationSer. No. 11/019,351, filed Dec. 23, 2004 (now U.S. Pat. No. 7,083,650).

U.S. application Ser. No. 11/943,334 is a Continuation of Ser. No.10/964,633, filed Oct. 15, 2004 and a Continuation-in-part of Ser. No.11/487,415, filed Jul. 17, 2006 (now U.S. Pat. No. 7,854,766) and U.S.application Ser. No. 11/019,351, filed Dec. 23, 2004 (now U.S. Pat. No.7,083,650).

U.S. application Ser. No. 11/487,415 is a Continuation of Ser. No.10/964,633, filed Oct. 15, 2004 and a Continuation-in-part of Ser. No.11/019,351, filed Dec. 23, 2004 (now U.S. Pat. No. 7,083,650, and claimspriority to 60/788,720, filed Apr. 4, 2006.

U.S. application Ser. No. 11/019,351 is a Continuation of Ser. No.10/964,633, filed Oct. 15, 2004, which claims priority to U.S.Application Nos. 60/570,098, filed May 12, 2004; 60/570,837, filed May14, 2004; 60/572,468, filed May 20, 2004; 60/573,346, filed May 24,2004; and 60/578,319, filed Jun. 10, 2004.

BACKGROUND

This description relates to a three piece mechanical total cervicalartificial disc, which includes two spiked cervical plates and a mobilecore. The disc may be inserted into the cervical intervertrebral discspace using a novel disc plate insertion gun which performs sequentialsingle plate intervertebral implantation enabling symmetric bi-discplate alignment for inter plate mobile core placement. This cervicaldisc design and method of implantation avoid the cumbersome and arduousimplantation techniques of many other artificial cervical disc designsimproving safety, improving bone-plate insertion/integration, allowingmultiple-level disc placement, preserving vertebral body integrity,eliminating the need for excessive disc space distraction, anddecreasing procedure length. This description also relates to a modifiedapplication of the disc plate inserter design from copending, relatedapplications describing posterior placed total artificial disc (PTTLAD).The modified disc plate inserter allows posterior lumbar sequentialplacement of two opposing disc plates rather than simultaneous two discplate placement as outlined in our previous publication. The modifieddisc plate inserter enables implantation of the PTTLAD into narrowerlumbar disc spaces which were not accessible with our previous lumbardisc plate inserter.

Cervical and lumbar discs are entering the clinical neurosurgical andorthopedic markets. The benefits of these artificial discs are wellknown and have been thoroughly reviewed in our prior and co-pendingprosthetic disc patents, including Provisional Application 60/788,720filed on Apr. 4, 2006, copending U.S. patent application Ser. No.11/019,351, filed on Dec. 23, 2004 and Ser. No. 10/964,633, filed onOct. 15, 2004, U.S. Provisional Application Nos. 60/578,319 filed onJun. 10, 2004, 60/573,346 filed on May 24, 2004, 60/572,468 filed on May20, 2004, 60/570,837 filed on May 14, 2004, and 60/570,098 filed on May12, 2004, and U.S. patent application Ser. No. 11/487,415 filed on Jul.17, 2006, the entire contents of each of which are hereby incorporatedby reference. In one or more of the foregoing applications, we describedfour different cervical artificial disc embodiments which expanded intwo or three-dimensions. This description presents an evolutionarysimplification of these embodiments, e.g., with fewer small parts, whichexpand in only one dimension, and can be inserted very simply andefficiently. Accordingly, the advanced cervical disc design of thepresent application is a geometric modification of previous lumbar discdesigns in one or more of the above-referenced patents, e.g., U.S.Patent Publication No. 2007/0198089 A1.

The cervical disc design of the present application differs fromapproaches of the background art which typically describe two-piecedesigns, e.g., as opposed to the three disc designs of the presentapplication. In the two-piece designs, one piece consists of either anupper or lower cervical disc plate with a central trough to accommodatethe opposing disc plate. The other piece, the opposing disc plate, hasan incorporated dome shaped immobile core. The immobilized core isstationary and does not move. Semi-constrained artificial motion occursas a result of the troughed plate movement against and around theimmobilized core.

One or more of these designs are described in the following exemplarypatent documents, including U.S. Pat. No. 5,314,477, filed Mar. 4, 1991(Thierry Marnay), entitled “Prosthesis for intervertebral discs andinstruments for implanting it;” U.S. Pat. No. 6,113,637 (Gill et al.),filed Oct. 22, 1998, entitled “Artificial intervertebral jointpermitting translational and rotational motion; U.S. Pat. No. 6,540,785B1 (Gill et al.) filed on Mar. 24, 2000, entitled “Artificialintervertebral joint permitting translational and rotational motion;”U.S. Pat. No. 6,8899,735 B2 (Bradley J Coates et. al.) filed on Oct. 2,2002, entitled “Modular intervertebral prosthesis system,” U.S. Pat. No.6,908,484 B2 (Zubok et. al.) filed on Mar. 6, 2003, entitled “Cervicaldisc replacement.” In each of the foregoing two-piece designs of thebackground art, the artificial implant is implanted within the vertebralbodies either by using attached hinges, keels or some form of extensionwhich accommodates placement of vertebral screws.

The present inventors have determined that one disadvantage of most ofthese systems is that placement of the prosthesis is arduous, and timeconsuming, and can destroy a substantial part of the vertebral bodyafter insertion of the device. The designs that use screws have thepotential risks of screw pull out and secondarily esophageal injury,screw breakage, and/or inability to perform multilevel disc placement.Furthermore the fact that these designs do not have a mobile core leadsto substantially constrained motion.

Similarly, U.S. Patent Publication No. 2007/0173936 A1 (Hester) filed onJan. 23, 2006, describes a design which includes spikes, also includes atwo-piece design with an immobilized core. One or more embodiments ofthe present application includes a mobile core which more closelysimulates natural semi-constrained motion of a healthy cervical disc.U.S. Patent Publication No. 2005/0021146 A1 (de Villiers et al.) filedMay 26, 2004 consists of two separate plates placed which are insertedsimultaneously as one unit, after which a mobile core is inserted inbetween the plates. However, the plates include keels which can damagevertebral bodies, and prevent multilevel placement. U.S. Pat. No.6,001,130 (Bryan), filed Oct. 6, 1997, describes a one piece design.However, the one-piece design involves an arduous placement techniqueinvolving disc space distraction, and the use of hinges and screws,limiting multi-level placement.

SUMMARY

One or more of the embodiments of the present application overcome oneor more of the above-described shortcomings of the background art. Forexample, a cervical disc design and tool for implantation of thecervical disc is an improvement over one or more of the above mentioneddesigns of the background art. Specifically, the spikes allowintegration into the vertebral body, e.g., with relatively small spikes,without damaging the vertebral bodies. This is particularly important iffuture prosthetic or fusions need to be performed at that level. Thecervical plates are inserted sequentially with a novel cervical plateinsertion gun. The advantage of the cervical plate insertion gun is thatthe method of implantation is quick and efficient. No disc spacedistraction is needed and hence there is no fear of damaging ordisarticulating posterior cervical facets. It can also be placed intonarrower spaces without distraction. The mobile core of the presentapplication also more closely approximates the natural semi-constrainedmotion of a healthy disc more so than the above mentioned discs.

Additional advantages of our posterior placed total lumbar artificialdisc (PTTLAD) lumbar disc design have been fully reviewed in ourco-pending patents, each of which have been incorporated by referenceherein. The present lumbar disc plate inserter design offers twoadditional advantages over previous embodiments. First, the inserterdesign grasps the plates more securely. In addition, the sequentialplacement of the different plates allows placement of posteriorartificial discs into narrower disc spaces.

In one general aspect, an artificial spinal disc includes a pair ofsubstantially parallel plates formed to occupy a space defined byvertebral endplates. Each of the plates including a plurality of spikeson a first surface and a concave trough formed on a second surfaceopposite of the first surface. A mobile core includes a core rim withopposing convex surfaces extending from opposite sides of the core rim,the mobile core being capable of being disposed between the pair ofplates to permit the vertebral endplates to move relative to oneanother. The spikes on each of the plates extend substantially away fromthe mobile core and the convex surfaces are formed to integrally fitwithin the concave trough of at least one of the plates. The core rimlimits lateral movement of the mobile core relative to the parallelplates.

Implementations of this aspect may include one or more of the followingfeatures. For example, the plates and mobile core can be sized andshaped to integrally fit within a space defined by cervical vertebralendplates and/or lumbar vertebral endplates. Each trough can be disposedin a center of each respective, parallel plate. The troughs can beshaped to receive the convex surfaces of the mobile core and the corerim can be shaped to receive outer edges of the troughs with an integralfit. The substantially parallel plates can include a plurality ofconically shaped spikes.

The mobile core rim may include at least a first substantially ringshaped member having a raised edge and a second substantially ringshaped member having a raised edge. The first and second ring shapedmembers may each define respective cavities where the convex surfacesare respectively positioned within and extend from. The plates cancomprise an elliptical shape.

In another general aspect, an artificial disc insertion system includesan artificial disc having a pair of substantially parallel plates formedto occupy a space defined by vertebral endplates, each of the platesincluding a plurality of spikes on a first surface and a concave troughformed on a second surface opposite of the first surface. The discincludes a mobile core having a core rim with opposing convex surfacesextending from opposite sides of the core rim, the mobile core beingcapable of being disposed between the pair of plates to permit thevertebral endplates to move relative to one another. The spikes on eachof the plates extend substantially away from the mobile core and theconvex surfaces are formed to integrally fit within the concave troughof at least one of the plates. The core rim limits lateral movement ofthe mobile core relative to the parallel plates. The system alsoincludes a surgical tool.

The surgical tool for inserting the artificial disc between vertebralendplates, the tool includes a handle portion having a trigger, an upperdisc plate release button, and a lower disc plate release button. Thesurgical tool also includes an insertion portion extending distally awayfrom the handle portion, the insertion portion includes an upperreplacement plate releasing portion and a lower replacement platereleasing portion. The upper replacement plate releasing portionincludes a release handle and a release link configured to engage andrelease a periphery of an upper replacement plate, e.g., to releasablysecure the upper replacement plate therebetween. The lower replacementplate releasing portion includes a release handle and a release linkconfigured to engage and release a periphery of a lower replacementplate, e.g., to releasably secure the lower replacement platetherebetween.

Implementations of this aspect may include one or more of the followingfeatures. For example, the mobile core and plates can be sized andshaped for a cervical disc replacement. The mobile core and the platescan be sized and shaped for a lumbar disc replacement. The mobile corerim may include at least a first substantially ring shaped member havinga raised edge and a second substantially ring shaped member having araised edge. The first and second ring shaped members may each definerespective cavities where the convex surfaces are respectivelypositioned within and extend from. The plates can include an ellipticalshape.

In another general aspect, a surgical tool for inserting an artificialdisc between vertebral endplates includes a handle portion comprising atrigger, an upper disc plate release button, and a lower disc platerelease button. The tool also includes an insertion portion extendingdistally away from the handle portion, the insertion portion comprisingan upper replacement plate releasing portion and a lower replacementplate releasing portion. The upper replacement plate releasing portionincludes a release handle and a release link configured to engage andrelease a periphery of an upper replacement plate, e.g., to releasablysecure the upper replacement plate therebetween. The lower replacementplate releasing portion includes a release handle and a release linkconfigured to engage a periphery of a lower replacement plate, e.g., toreleasably secure the lower replacement plate therebetween.

Implementations of this aspect may include one or more of the followingfeatures. For example, the insertion portion may include an upper tipportion and a lower tip portion. The upper tip portion and the lower tipportion may be curved to facilitate posterior insertion of a lumbarreplacement disc in a patient. At least one of the upper or lowerreplacement plate releasing portions can include a leaf spring, atension cable and a wedge portion proximally disposed relative to therespective release handle and the release link. Each of the upper andlower replacement plate releasing portions can include a leaf spring, atension cable and a wedge portion proximally disposed relative to therespective release handle and the release link. The tool can include areplacement disc plate driver portion for driving a replacement discplate from a first, proximal position toward a second, distal position.The upper replacement plate releasing portion is configured to secure anupper replacement plate in a position opposite from and axially alignedwith a center of a lower replacement plate held within the lowerreplacement releasing portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an anterior (or posterior) view of an exemplary cervicalartificial disc.

FIG. 1B is an isometric view of the cervical artificial disc of FIG. 1A.

FIG. 1C is an exploded view of the cervical artificial disc of FIG. 1A.

FIG. 1D is a superior (or inferior) view of the cervical artificial discof FIG. 1A.

FIG. 2A is a side view of an exemplary cervical artificial disc mobilecore.

FIG. 2B is an isometric view of the exemplary cervical artificial discmobile core.

FIG. 2C is a front (or back) view of the exemplary cervical artificialdisc mobile core.

FIG. 3A is a side view of an exemplary cervical artificial disc superioror inferior plate.

FIG. 3B is a top oblique-trough side view of the exemplary cervicalartificial disc superior or inferior plate.

FIG. 3C is a top oblique-spike view of the exemplary cervical artificialdisc superior or inferior plate.

FIG. 3D is a front-trough side view of the exemplary cervical artificialdisc superior or inferior plate.

FIG. 3E is a front-spike side view of the exemplary cervical artificialdisc superior or inferior plate.

FIG. 4A is a cross-sectional view of a cervical disc core showing theangular movements about the x-axis of the cervical disc core withrespect to the upper and lower cervical plates (lateral bending).

FIG. 4Bi is a front view of later cervical disc bending.

FIG. 4Bii is a side view of flexion/extension cervical artificial discmotion.

FIG. 4Ci is a front view of the artificial disc showing the rotations ofthe mobile core between the two cervical disc plates about the x-axis(lateral bending or roll).

FIG. 4Cii is a side view of the artificial disc showing the y-axis(flexion/extension or pitch).

FIG. 4Ciii is a perspective view of the artificial disc showing thez-axis (rotation or yaw).

FIG. 5A is a front view of a cervical disc plate insertion gun.

FIG. 5B is a top view of the cervical disc plate insertion gun.

FIG. 5C is a bottom view of the cervical disc plate insertion gun.

FIG. 6A is a perspective, left-side, cut-away view of the cervical discplate insertion gun.

FIG. 6B is a left side, bottom angle view of the cervical disc plateinsertion gun.

FIG. 6C is a right side, top angle view of the cervical disc plateinsertion gun.

FIG. 6D is a right side, bottom angle view of the cervical disc plateinsertion gun.

FIG. 6E is a cut-away view of the tool tip lower cervical discreplacement plate release mechanism.

FIG. 7A is a view of an outside left enclosure of the cervical discplate insertion gun.

FIG. 7B is a view of an inside left enclosure of the cervical disc plateinsertion gun.

FIG. 7C is a view of an outside right enclosure of the cervical discplate insertion gun.

FIG. 7D is a view of an inside right enclosure of the cervical discplate insertion gun.

FIG. 8A is a top view of inner components of the cervical plateinsertion gun including the lower insertion handle.

FIG. 8B is a lower insertion handle bottom view.

FIG. 8C is top view of a lower insertion link.

FIG. 8D is bottom view of the lower insertion link.

FIG. 8E is a view of the wedge link.

FIG. 8F is a top view of the upper insertion handle.

FIG. 8G is a lower view of the upper insertion handle lower view.

FIG. 8H is a close-up bottom view of a rear portion of the upperinsertion handle.

FIG. 8I is a close-up, top view of a forward portion of the upperinsertion handle.

FIG. 8J is a top view from left of the upper insertion release link.

FIG. 8K is a top view from a right side of the upper insertion link.

FIG. 8L is a view of a manual upper disc replacement plate driver.

FIG. 8M is a view of a trigger spring.

FIG. 8N is a view of a trigger.

FIG. 8O is a view of a wedge.

FIG. 9A is a perspective cut away view of an exemplary lumbar disc platinsertion gun.

FIG. 9B is a cut-away view of the tool tip of the lower lumbar discreplacement plate release mechanism.

DESCRIPTION OF PREFERRED EMBODIMENTS The Medical Device of FIG. 1-9

Referring now to FIGS. 1-9, the above described problems of thebackground art can be solved in the cervical spine (and lumbar spine)after the performance of an anterior complete cervical discectomy. Thedisc device 10 includes an upper cervical plate 100 and lower cervicalplate 110, one of which is inserted first by a plate insertion gun 500.The opposite (second) cervical disc plate 110 is then inserted with theplate insertion gun 500 maintaining parallel opposition, with oppositeplates 100, 110 and troughs 102, 112 perfectly aligned. A mobile core150 is then inserted and sandwiched in-between both cervical plates 100,110.

FIGS. 1A-D illustrate different views of the cervical artificial disc10. The disc 10 includes an upper plate 100 and a lower plate 110. Eachplate has a plurality of spikes 101, 111, e.g., six spikes 101, 111 oneach plate in a preferred embodiment, on an outer surface of therespective plate, and a centralized trough 102, 112 on an inner surfaceof each plate 100, 110.

FIGS. 2A-C illustrate different views of the cervical mobile core 150.The core 150 has a centralized base rim 151 with a superior convexity152 which interacts with the trough 102 of the upper plate 100, and aninferior convexity 153 which interacts with the trough 112 of the lowerplate 110.

FIGS. 3A-E illustrate different views of the cervical plate (superior orinferior) 100 (110). The plate 100 includes a base 114. On an uppersurface of the inferior plate 110 is a trough 112. On a lower surface ofthe inferior plate 110 are 6 peripherally arranged spikes 111. Theposition of the trough 112 and spikes 111 are reversed for the superiorplate (100). A groove 113 is defined by the trough 112 (102) and base114 (104) of each plate 110 (100).

FIG. 4A illustrates a cross-sectional view of the cervical artificialdisc 10 and the degrees of motion of the mobile core 150 movement aboutthe x-axis with respect to the upper plate 100 and lower plate 110. Eachdisc plate 100 can bend about the x axis by 4.39 degrees clockwise andcounter-clockwise (lateral bending). This means that a disc plate 100,110 can move − or +8.78 degrees with respect to the opposite plate 110,100.

FIG. 4B illustrates a front view of lateral bending of the artificialdisc 10 (FIG. 4Bi), and a side view illustrating flexion-extension ofthe cervical disc 10 about the y axis which is 4.39 degrees in eitherflexion or extension.

FIG. 4C illustrates the rotation of the mobile core 150 between twocervical plates 100, 110 about the x (FIG. 4Ci), y (FIG. 4Cii) and z(FIG. 4Ciii) axes. Rotation about the x-axis is referred to as roll(alpha) which is lateral bending. Rotation about the y axis is referredto as pitch (Beta) which is flexion/extension. Rotation about the z axisis referred to as yaw (gamma) which is axial rotation. These figuresdisplay different views that show a reference frame for the discassembly 10 with an origin O at the center of the core 150. The axes ofrotation pass through the spherical face of the core 150 which is lowerthan 0 but are parallel to both the x and y axes. The rotation of thedisc plates 100, 110 about the z-axis is constrained only by the spinemotions once the disc 10 is implanted.

FIGS. 5-8 illustrate the components of the cervical disc plate insertiongun 500. Various opening mechanism functions will be described ingreater detail hereinafter with respect to FIGS. 5-8. The handle 512 ofthe opening mechanism is made up of left and right enclosures 501, 502(FIGS. 5, 6, and 7). FIG. 7 illustrates the inside and outside aspectsof left and right enclosures 501, 502. These enclosures 501, 502 areheld together by five enclosure fastening screws 590 (FIG. 6B). Thehandle 512 holds the mechanism used to insert the upper disc plate 100and lower disc plate 110 (FIGS. 5-6, and FIG. 8) into the vertebrae. Themechanism has two functions, including: 1) Holding onto the disc plates100, 110 until the user releases them, and 2) opening the tip 560 andforcing one disc plate at a time into a vertebra.

1. Holding Onto the Discs Until User Releases Them

The mechanism has two tips 565, 580 each holding a disc plate 100, 110.The lower tip 580 is composed of two parts: the lower insertion releaselink 576 and the lower insertion release handle 551 (FIGS. 6 and 8). Theupper tip 565 includes two parts: the upper insertion handle 550 and theupper insertion link 575 (FIGS. 6 and 8). Each tip 565, 580 works like a“lobster claw” that holds a disc plate by the “groove” 552 on itscylindrical extrusion. When the tip 565, 580 is closed the two opposingparts e.g. the lower insertion release link 576 and the lower insertionrelease handle 551 (FIGS. 6 and 8) hold a disc plate 110 firmly.

A tip 580 opens to release a disc plate as follows. A lower tensioncable 571 pulls on the lower insertion release link 576 (FIGS. 6 and 8)that pivots about the lower release pin 598 (FIG. 6) and opens up a gapbig enough to loosen the grip on the disc groove 552. The lower tensioncable 571 (FIG. 6) can only exert a tensile force to open the lobsterclaw 580. The natural state of the lobster claw 580 is to be closed.This is ensured by pre-loading the lower insertion release link 576 withthe help of a leaf spring 599 cut into the lower insertion releasehandle 551 (FIGS. 6E and 8). The lower tension cable 571 pulls on thelower insertion release link 576 (FIGS. 6 and 8) each time the userpresses on the lower release button 540. The lower tension cable 571 isclamped on one end by a lower rear crimp 592 (FIGS. 6 and 8). Hence whenthe lower release button 540 is pressed, the tension on the lowertension cable 571 increases (in the same way the tension of a guitarstring increase when one presses on the string with a finger). Thetension then pulls the lower insertion release link 576 forcing it toswing open. When the user lets go of the button 540, the tensiondisappears and the spring 599 carved in the lower insertion releasehandle 551 forces the lower insertion release link 576 to swing closed(FIG. 6E).

The upper tip 565 works in a similar fashion except that its opening istriggered by the upper release button 530.

2. Opening Its Tip and Forcing One Disc at a Time Into a Vertebra

The mechanism tips 565, 580 open each time the user presses on trigger510. When the trigger 510 rotates, it pushes on the wedge link 513 whichin turn pushes on the wedge part 525 (FIG. 8). The wedge part 525 iswedged at its front action end that creates a gap in between the lowertool tip 580 and upper tool tip 565 forcing them to open.

A typical disc insertion operation starts with a lower disc plate 110placed in the lower tip 580 and the opposing upper disc plate 100 placedon the upper side but away from the tip 565 (as shown in FIGS. 5, 6, and8). A channel 553 along the upper tip 565 that is formed by the upperinsertion release handle 550 and the upper insertion release link 575which holds the second disc plate 100 in place and serves to guide it tothe tip 565 when needed.

Once the tool tip 560 is inserted into the inter-vertebral space, thefirst disc plate 100 is inserted into the lower vertebra by opening thetool tip 560. To keep alignment, the lower tool tip 585, “lower lobsterclaw”, is kept closed (FIG. 6), securing the disc plate just inserted.The tool 500 should be left in place. The second, upper, disc 100initially placed in the upper tool half, away from the “upper lobsterclaw” 565 but away from the tip is then slid down to the end of theupper lobster claw 565 by a flexible and manually activated upper discreplacement plate driver 520 (FIGS. 6 and 8). Once the second disc 100is positioned at the tip of the upper “lobster claw” 565 (FIG. 6), thetool tip 560 is opened once more, i.e., the upper tip 565 and lowerlobster claw tip 580 are separated from each other, by virtue of thewedge 525 that is activated by the trigger 510, via wedge link 513action. Once the second, upper, disc plate 100 is inserted, the user canpress on the upper release button 530 and lower release button 540 torelease both discs (by opening the upper and lower “lobster claws” 565,580) and at the same time close the tool tip 560 (by releasing thetrigger 510). The tool tip 560 then closes while both “lobster claws”565, 580 remain open, leaving both disc plates 100, 110 in place. Thetool tip 560 can then be removed from the patient and a mobile coreplaced in between the two aligned disc plates 100, 110.

This anterior cervical disc gun can be modified and enlarged forplacement of anterior lumbar disc plates. FIG. 9A illustrates themodified posterior lumbar disc plate insertion gun 700. The gun 700 isidentical to the cervical disc plate insertion gun 500 except its tips660 are angled to allow insertion of the specifically sized lumbar discplates 100, 110 in the posterior lumbar spine underneath the thecal sac.

FIG. 9B illustrates an enlarged cut-away view of the tool tip 660 of thelumbar lower disc replacement plate release mechanism 670. The mechanism670 is identical to that described for the cervical mechanism which isillustrated FIG. 6E. The tips 660 of the lumbar tool are however,specifically designed and adapted for the typically bean shaped lumbardisc plates.

The Surgical Method

The method of insertion of the cervical artificial disc (or lumbarartificial disc) into the anterior cervical spine can be performed openmicroscopically, or closed tubularly, using endoscopic and/orfluoroscopic guidance.

After the adequate induction of anesthesia the patient is positioned inthe supine position. Routine exposure of the anterior cervical spine isperformed and the appropriate disc space is radiographically identifiedand exposed. A routine complete anterior cervical discectomy isperformed.

The cervical disc plates are inserted onto the cervical disc plateinsertion gun 500. The tips 560 of the gun 500 are placed into theintervertebral space. Fluoroscopy is used to assure centrality of discplate placement.

The trigger 510 of the gun 500 is depressed and the bottom plate 110 isinserted into the lower vertebrae. Once this penetrates the bone, thelower plate releasing button 540 is depressed, thereby releasing theplate from the inserter claws 580 (FIG. 6E). The second upper plate 100is now manually driven into the space by the gun's manual plate driver520. Because of the design of the gun 500, the upper plate 100 isperfectly aligned with the lower plate 110. The gun trigger 510 isdepressed and this drives the upper plate 100 into the upper vertebrae.The upper plate releasing button 530 is now depressed, releasing theupper plate 100 from the inserter lobster claws 565. The gun 500 isremoved from the interspace. A mobile core 150 of the appropriate heightis selected and placed in between the upper and lower cervical discplates 100, 110, respectively. The patient is closed routinely.

The surgical method for the posterior insertion of the PPLTAD into theposterior lumbar interspace can be performed open microscopically, orclosed tubularly, using endoscopic and or fluoroscopic guidance.

After the adequate induction of anesthesia the patient is positioned inthe prone position. A midline incision is made, the appropriateunilateral lamina is radiographically identified and exposed, and aunilateral hemi-laminotomy is performed preserving facet stability. Acomplete discectomy is performed, and the superior and inferiorendplates are exposed. The lumbar pplate insertion gun 700 is placedunderneath the thecal sac. Fluoroscopic guidance may be used to verifycentrality of lumbar disc plate placement. The trigger of the gun 700 isdepressed which leads to insertion of the lower lumbar disc plate 100into the lower vertebra. The lower lumbar disc plate releasing button isdepressed which releases the plate from the inserter claws 551 (FIG.9B). The second upper plate 100 is now manually driven into theinterspace by the gun's 700 manual plate driver (520). Because of thedesign of the gun mechanism as described above, the second plate 100 isnow perfectly aligned with the first lumbar disc plate 110. The guntrigger is depressed, and this drives the upper plate 100 into the uppervertebrae. The upper lumbar disc plate release button is now depressedand this releases the upper lumbar disc plate from the claws of theinserter gun 700. The gun 700 is removed from the space. Anappropriately sized mobile core 150 is now inserted in between upper andlower lumbar disc plates 100, 110. The patient is closed routinely.

The current device allows safe placement of lumbar and cervicalartificial discs into the spine without intervertebral distraction, andtherefore places minimal tension on facet joints. The method ofinsertion is quick, gentle, and time efficient. The plate insertion guncould potentially be adapted for other inter joint orthopedic devices,and further adaptations may have applications in manufacturing, toy,carpentry and other industries.

What is claimed is:
 1. An artificial disc system comprising: anartificial disc comprising: first and second plates formed to occupy aspace defined by vertebral endplates of a spine, each of the first andsecond plates including an endplate-engaging surface having plurality ofanchors and a core-engaging surface positioned opposite theendplate-engaging surface, wherein the plurality of anchors on theendplate-engaging surface of the first plate comprise a first group ofat least three anchors on a left side of the first plate and a secondgroup of at least three anchors on a right side of the first plate witha middle portion of the first plate having no anchors between the firstand second groups of anchors, wherein the first group of at least threeanchors comprises first, second, and third anchors that are aligned withthe second anchor positioned between the first and third anchors along afirst curved line such that the second anchor is positioned further froma midline of the first plate than are the first and third anchors,wherein the second group of at least three anchors comprises fourth,fifth, and sixth anchors that are aligned with the fifth anchorpositioned between the fourth and sixth anchors along a second curvedline such that the fifth anchor is positioned further from the midlineof the first plate than are the fourth and sixth anchors, wherein theplurality of anchors on the endplate-engaging surface of the secondplate comprise a third group of at least three anchors on a left side ofthe second plate and a fourth group of at least three anchors on a rightside of the second plate with a middle portion of the second platehaving no anchors between the third and fourth groups of anchors,wherein the third group of at least three anchors comprises seventh,eighth, and ninth anchors that are aligned with the eighth anchorpositioned between the seventh and ninth anchors along a third curvedline such that the eighth anchor is positioned further from a midline ofthe second plate than are the seventh and ninth anchors, wherein thefourth group of at least three anchors comprises tenth, eleventh, andtwelfth anchors that are aligned with the eleventh anchor positionedbetween the tenth and twelfth anchors along a fourth curved line suchthat the eleventh anchor is positioned further from the midline of thesecond plate than are the tenth and twelfth anchors, wherein thecore-engaging surface of the first plate is substantially concave; and amobile core sized and configured to be positioned between the first andsecond plates to permit the first and second plates to move relative toone another, wherein the anchors on the endplate-engaging surfacesextend substantially away from the mobile core, wherein thecore-engaging surfaces engage first and second plate-engaging surfacesof the mobile core, wherein both of the first and second plate-engagingsurfaces are configured to slide against adjacent core-engaging surfacesof the first and second plate, wherein the first plate-engaging surfaceof the mobile core has a convex spherical dome portion shaped to matewith the concave core-engaging surface of the first plate, and whereinthe mobile core is engaged with the first and second plates such thatthe first plate can move with respect to the second plate about anx-axis for lateral bending, a y-axis for flexion/extension, and a z-axisfor axial spinal rotation, wherein the mobile core is sized large enoughthat at least a perimeter edge of the mobile core is configured toextend partially out of a space defined between perimeter edges of thefirst and second plates when the artificial disc is tiled about they-axis for flexion or extension.
 2. The artificial disc system of claim1, wherein the convex spherical dome portion of the first plate-engagingsurface of the mobile core has a first height and a first radius withfirst height less than the first radius, wherein the mobile core has aradially outer portion that is positioned radially outward of the convexspherical dome portion, and wherein the core-engaging surface of thefirst plate has a convex spherical dome portion with a second height anda second radius with the second height less than the second radius. 3.The artificial disc system of claim 1, wherein the mobile core has afirst width along the x-axis from a core front to a core back and asecond width along the y-axis from a first core side to a second coreside, and wherein the second width is equal to the first width.
 4. Theartificial disc system of claim 1, wherein the mobile core has a firstwidth along the x-axis from a core front to a core back and a secondwidth along the y-axis from a first core side to a second core side, andwherein the second width is at least as great as the first width.
 5. Theartificial disc system of claim 1, wherein the first and second platesare configured to move with respect to the mobile core to have asubstantially parallel orientation as well as a plurality of nonparallelorientations.
 6. The artificial disc system of claim 1, wherein thefirst plate can tilt with respect to the second plate by over 8 degreeswith respect to each of the x-axis and the y-axis.
 7. The artificialdisc system of claim 1, wherein the mobile core comprises a rimconfigured to engage a projecting portion on at least one of the firstand second plates to limit movement of the mobile core with respect tothe at least one of the first and second plates.
 8. The artificial discsystem of claim 1, wherein the artificial disc is sized and configuredto be a cervical artificial disc to be inserted in a cervical discspace.
 9. The artificial disc system of claim 1, wherein one or moreanchors of the first group of at least three anchors, one or moreanchors of the second group of at least three anchors, one or moreanchors of the third group of at least three anchors, and one or moreanchors of the fourth group of at least three anchors are symmetric whenviewed along the x-axis.
 10. The artificial disc system of claim 1,wherein one or more anchors of the first group of at least threeanchors, one or more anchors of the second group of at least threeanchors, one or more anchors of the third group of at least threeanchors, and one or more anchors of the fourth group of at least threeanchors are symmetric when viewed along the z-axis.
 11. The artificialdisc system of claim 1, wherein one or more anchors of the first groupof at least three anchors, one or more anchors of the second group of atleast three anchors, one or more anchors of the third group of at leastthree anchors, and one or more anchors of the fourth group of at leastthree anchors are symmetric when viewed along the y-axis.
 12. Theartificial disc system of claim 1, wherein the endplate-engaging surfaceof the second plate is flat between the third group of at least threeanchors and the fourth group of at least three anchors.
 13. Theartificial disc system of claim 1, wherein the endplate-engaging surfaceof the second plate has no raised surface features between the thirdgroup of at least three anchors and the fourth group of at least threeanchors.
 14. The artificial disc system of claim 1, wherein the anchorscomprise spikes.
 15. The artificial disc system of claim 1, wherein themobile core comprises means to limit movement of the mobile core withrespect to at least one of the first and second plates.
 16. Anartificial disc system comprising: an artificial disc comprising: firstand second plates formed to occupy a space defined by vertebralendplates of a spine, each of the first and second plates including anendplate-engaging surface having plurality of anchors and acore-engaging surface positioned opposite the endplate-engaging surface;and a mobile core sized and configured to be positioned between thefirst and second plates to permit the first and second plates to moverelative to one another, wherein the anchors on the endplate-engagingsurface extend substantially away from the mobile core and thecore-engaging surfaces engage first and second plate-engaging surfacesof the mobile core, wherein both of the first and second plate-engagingsurfaces are configured to slide against adjacent core-engaging surfacesof the first and second plate and wherein at least one of the first andsecond plate-engaging surfaces of the mobile core is substantiallyconvex such that the first plate can move with respect to the secondplate about an x-axis for lateral bending, a y-axis forflexion/extension, and a z-axis for axial rotation of the spine, whereinthe core-engaging surface of the first plate is substantially concaveand is sized and shaped for engaging a convex portion of the firstplate-engaging surface of the mobile core, wherein the plurality ofanchors on the endplate-engaging surface of the first plate comprise afirst group of anchors on a left side of the first plate and a secondgroup of anchors on a right side of the first plate with a middleportion of the first plate having no anchors between the first andsecond groups of anchors, wherein the first group of anchors comprisesfirst, second, and third anchors that are aligned with the second anchorpositioned between the first and third anchors along a first curved linesuch that the second anchor is positioned further from a midline of thefirst plate than are the first and third anchors, wherein the secondgroup of anchors comprises fourth, fifth, and sixth anchors that arealigned with the fifth anchor positioned between the fourth and sixthanchors along a second curved line such that the fifth anchor ispositioned further from the midline of the first plate than are thefourth and sixth anchors, wherein the plurality of anchors on theendplate-engaging surface of the second plate comprise a third group ofanchors on a left side of the second plate and a fourth group of anchorson a right side of the second plate with a middle portion of the secondplate having no anchors between the third and fourth groups of anchors,wherein the third group of anchors comprises seventh, eighth, and ninthanchors that are aligned with the eighth anchor positioned between theseventh and ninth anchors along a third curved line such that the eighthanchor is positioned further from a midline of the second plate than arethe seventh and ninth anchors, wherein the fourth group of anchorscomprises tenth, eleventh, and twelfth anchors that are aligned with theeleventh anchor positioned between the tenth and twelfth anchors along afourth curved line such that the eleventh anchor is positioned furtherfrom the midline of the second plate than are the tenth and twelfthanchors; and a surgical tool for inserting the artificial disc betweenvertebral endplates, the surgical tool comprising: a handle; an elongateinsertion portion extending distally away from the handle; and animplant holder connected at a distal end of the elongate insertionportion and having first and second tips sized and configured to engagethe first and second plates so as to hold both the first and secondplates relatively firmly during insertion and positioning of the firstand second plates in the space defined by the vertebral endplates of thespine, wherein first and second tips of the implant holder comprise aclaw having first and second curved portions that engage the first plateto hold the first plate, wherein the first curved portion of the claw ismovable with respect to the second curved portion of the claw so as torelease the first plate when the claw is opened.
 17. The artificial discsystem of claim 16, wherein the claw is biased to a closed position in anatural state to hold the first plate and the claw releases the firstplate only in response to a force exerted to open the claw.
 18. Theartificial disc system of claim 16, wherein the claw comprises a springthat pre-loads the claw to bias the claw to a closed position to holdthe first plate.
 19. The artificial disc system of claim 16, wherein thesurgical tool attaches to the first and second plates without engagingthe mobile core.
 20. The artificial disc system of claim 16, whereincurved portion of the core-engaging surface of the first plate comprisesa concave portion, wherein the core-engaging surface further comprises asubstantially flat portion extending circumferentially around theconcave portion of the core-engaging surface of the first plate.